Electroluminescence (EL) is the emission of light under electric-field excitation. Based on this mechanism, EL lamps and displays are finding an increasing number of applications in the field of flat panel displays due to the growing demand for portable computers, communication equipment, and consumer electronic products. EL lamps also provide uniform light emission independent of viewing angle and they are insensitive to mechanical shock and vibration.
The two major EL lamp constructions are generally referred to as thin-film and thick-film. Thin-film EL lamps are made by depositing alternating thin layers of dielectric materials, phosphors and conductive oxides on a glass substrate using a vapor deposition technique such as CVD. By contrast, thick-film lamps are made by suspending powders in resinous materials and then applying them in layers onto a plastic film using conventional screen printing techniques. Hence, thick-film EL lamps can be thin, flexible and rugged thereby making them suitable for a wider range of lighting applications.
Most commonly, electroluminescent phosphors for thick-film applications are blue, blue-green, green or orange emitting. European Patent No. EP 1 006 170 B1 describes an electroluminescent phosphor with an emission spectrum having average CIE x,y color coordinates of 0.150 and 0.080, respectively.